/**
 * \file asn1.h
 *
 * \brief Generic ASN.1 parsing
 *
 *  Copyright (C) 2006-2013, Brainspark B.V.
 *
 *  This file is part of PolarSSL (http://www.polarssl.org)
 *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
 *
 *  All rights reserved.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#ifndef POLARSSL_ASN1_H
#define POLARSSL_ASN1_H

#include "config.h"

#if defined(POLARSSL_BIGNUM_C)
#include "bignum.h"
#endif

#include <string.h>

/** 
 * \addtogroup asn1_module
 * \{ 
 */
 
/**
 * \name ASN1 Error codes
 * These error codes are OR'ed to X509 error codes for
 * higher error granularity. 
 * ASN1 is a standard to specify data structures.
 * \{
 */
#define POLARSSL_ERR_ASN1_OUT_OF_DATA                      -0x0060  /**< Out of data when parsing an ASN1 data structure. */
#define POLARSSL_ERR_ASN1_UNEXPECTED_TAG                   -0x0062  /**< ASN1 tag was of an unexpected value. */
#define POLARSSL_ERR_ASN1_INVALID_LENGTH                   -0x0064  /**< Error when trying to determine the length or invalid length. */
#define POLARSSL_ERR_ASN1_LENGTH_MISMATCH                  -0x0066  /**< Actual length differs from expected length. */
#define POLARSSL_ERR_ASN1_INVALID_DATA                     -0x0068  /**< Data is invalid. (not used) */
#define POLARSSL_ERR_ASN1_MALLOC_FAILED                    -0x006A  /**< Memory allocation failed */
#define POLARSSL_ERR_ASN1_BUF_TOO_SMALL                    -0x006C  /**< Buffer too small when writing ASN.1 data structure. */

/* \} name */

/**
 * \name DER constants
 * These constants comply with DER encoded the ANS1 type tags.
 * DER encoding uses hexadecimal representation.
 * An example DER sequence is:\n
 * - 0x02 -- tag indicating INTEGER
 * - 0x01 -- length in octets
 * - 0x05 -- value
 * Such sequences are typically read into \c ::x509_buf.
 * \{
 */
#define ASN1_BOOLEAN                 0x01
#define ASN1_INTEGER                 0x02
#define ASN1_BIT_STRING              0x03
#define ASN1_OCTET_STRING            0x04
#define ASN1_NULL                    0x05
#define ASN1_OID                     0x06
#define ASN1_UTF8_STRING             0x0C
#define ASN1_SEQUENCE                0x10
#define ASN1_SET                     0x11
#define ASN1_PRINTABLE_STRING        0x13
#define ASN1_T61_STRING              0x14
#define ASN1_IA5_STRING              0x16
#define ASN1_UTC_TIME                0x17
#define ASN1_GENERALIZED_TIME        0x18
#define ASN1_UNIVERSAL_STRING        0x1C
#define ASN1_BMP_STRING              0x1E
#define ASN1_PRIMITIVE               0x00
#define ASN1_CONSTRUCTED             0x20
#define ASN1_CONTEXT_SPECIFIC        0x80
/* \} name */
/* \} addtogroup asn1_module */

/** Returns the size of the binary string, without the trailing \\0 */
#define OID_SIZE(x) (sizeof(x) - 1)

/** Compares two asn1_buf structures for the same OID. Only works for
 *  'defined' oid_str values (OID_HMAC_SHA1), you cannot use a 'unsigned
 *  char *oid' here!
 */
#define OID_CMP(oid_str, oid_buf)                                   \
        ( ( OID_SIZE(oid_str) == (oid_buf)->len ) &&                \
          memcmp( (oid_str), (oid_buf)->p, (oid_buf)->len) == 0 )

#ifdef __cplusplus
extern "C" {
#endif

/**
 * \name Functions to parse ASN.1 data structures
 * \{
 */

/**
 * Type-length-value structure that allows for ASN1 using DER.
 */
typedef struct _asn1_buf
{
    int tag;                /**< ASN1 type, e.g. ASN1_UTF8_STRING. */
    size_t len;             /**< ASN1 length, e.g. in octets. */
    unsigned char *p;       /**< ASN1 data, e.g. in ASCII. */
}
asn1_buf;

/**
 * Container for ASN1 bit strings.
 */
typedef struct _asn1_bitstring
{
    size_t len;                 /**< ASN1 length, e.g. in octets. */
    unsigned char unused_bits;  /**< Number of unused bits at the end of the string */
    unsigned char *p;           /**< Raw ASN1 data for the bit string */
}
asn1_bitstring;

/**
 * Container for a sequence of ASN.1 items
 */
typedef struct _asn1_sequence
{
    asn1_buf buf;                   /**< Buffer containing the given ASN.1 item. */
    struct _asn1_sequence *next;    /**< The next entry in the sequence. */
}
asn1_sequence;

/**
 * Container for a sequence or list of 'named' ASN.1 data items
 */
typedef struct _asn1_named_data
{
    asn1_buf oid;                   /**< The object identifier. */
    asn1_buf val;                   /**< The named value. */
    struct _asn1_named_data *next;  /**< The next entry in the sequence. */
}
asn1_named_data;

/**
 * \brief       Get the length of an ASN.1 element.
 *              Updates the pointer to immediately behind the length.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param len   The variable that will receive the value
 *
 * \return      0 if successful, POLARSSL_ERR_ASN1_OUT_OF_DATA on reaching
 *              end of data, POLARSSL_ERR_ASN1_INVALID_LENGTH if length is
 *              unparseable.
 */
int asn1_get_len( unsigned char **p,
                  const unsigned char *end,
                  size_t *len );

/**
 * \brief       Get the tag and length of the tag. Check for the requested tag.
 *              Updates the pointer to immediately behind the tag and length.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param len   The variable that will receive the length
 * \param tag   The expected tag
 *
 * \return      0 if successful, POLARSSL_ERR_ASN1_UNEXPECTED_TAG if tag did
 *              not match requested tag, or another specific ASN.1 error code.
 */
int asn1_get_tag( unsigned char **p,
                  const unsigned char *end,
                  size_t *len, int tag );

/**
 * \brief       Retrieve a boolean ASN.1 tag and its value.
 *              Updates the pointer to immediately behind the full tag.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param val   The variable that will receive the value
 *
 * \return      0 if successful or a specific ASN.1 error code.
 */
int asn1_get_bool( unsigned char **p,
                   const unsigned char *end,
                   int *val );

/**
 * \brief       Retrieve an integer ASN.1 tag and its value.
 *              Updates the pointer to immediately behind the full tag.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param val   The variable that will receive the value
 *
 * \return      0 if successful or a specific ASN.1 error code.
 */
int asn1_get_int( unsigned char **p,
                  const unsigned char *end,
                  int *val );

/**
 * \brief       Retrieve a bitstring ASN.1 tag and its value.
 *              Updates the pointer to immediately behind the full tag.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param bs    The variable that will receive the value
 *
 * \return      0 if successful or a specific ASN.1 error code.
 */
int asn1_get_bitstring( unsigned char **p, const unsigned char *end,
                        asn1_bitstring *bs);

/**
 * \brief       Retrieve a bitstring ASN.1 tag without unused bits and its
 *              value.
 *              Updates the pointer to the beginning of the bit/octet string.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param len   Length of the actual bit/octect string in bytes
 *
 * \return      0 if successful or a specific ASN.1 error code.
 */
int asn1_get_bitstring_null( unsigned char **p, const unsigned char *end,
                             size_t *len );

/**
 * \brief       Parses and splits an ASN.1 "SEQUENCE OF <tag>"
 *              Updated the pointer to immediately behind the full sequence tag.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param cur   First variable in the chain to fill
 * \param tag   Type of sequence
 *
 * \return      0 if successful or a specific ASN.1 error code.
 */
int asn1_get_sequence_of( unsigned char **p,
                          const unsigned char *end,
                          asn1_sequence *cur,
                          int tag);

#if defined(POLARSSL_BIGNUM_C)
/**
 * \brief       Retrieve a MPI value from an integer ASN.1 tag.
 *              Updates the pointer to immediately behind the full tag.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param X     The MPI that will receive the value
 *
 * \return      0 if successful or a specific ASN.1 or MPI error code.
 */
int asn1_get_mpi( unsigned char **p,
                  const unsigned char *end,
                  mpi *X );
#endif

/**
 * \brief       Retrieve an AlgorithmIdentifier ASN.1 sequence.
 *              Updates the pointer to immediately behind the full
 *              AlgorithmIdentifier.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param alg   The buffer to receive the OID
 * \param params The buffer to receive the params (if any)
 *
 * \return      0 if successful or a specific ASN.1 or MPI error code.
 */
int asn1_get_alg( unsigned char **p,
                  const unsigned char *end,
                  asn1_buf *alg, asn1_buf *params );

/**
 * \brief       Retrieve an AlgorithmIdentifier ASN.1 sequence with NULL or no
 *              params.
 *              Updates the pointer to immediately behind the full
 *              AlgorithmIdentifier.
 *
 * \param p     The position in the ASN.1 data
 * \param end   End of data
 * \param alg   The buffer to receive the OID
 *
 * \return      0 if successful or a specific ASN.1 or MPI error code.
 */
int asn1_get_alg_null( unsigned char **p,
                       const unsigned char *end,
                       asn1_buf *alg );

/**
 * \brief       Find a specific named_data entry in a sequence or list based on
 *              the OID.
 *
 * \param list  The list to seek through
 * \param oid   The OID to look for
 * \param len   Size of the OID
 *
 * \return      NULL if not found, or a pointer to the existing entry.
 */
asn1_named_data *asn1_find_named_data( asn1_named_data *list,
                                       const char *oid, size_t len );

/**
 * \brief       Free a asn1_named_data entry
 *
 * \param entry The named data entry to free
 */
void asn1_free_named_data( asn1_named_data *entry );

/**
 * \brief       Free all entries in a asn1_named_data list
 *              Head will be set to NULL
 *
 * \param head  Pointer to the head of the list of named data entries to free
 */
void asn1_free_named_data_list( asn1_named_data **head );

#ifdef __cplusplus
}
#endif

#endif /* asn1.h */
